1. Field of the Invention
This invention relates to a clutch operating apparatus having a control valve for controlling pressure oil to connect and disconnect the clutch, a clutch pedal supported to be pivotable, a bracket pivotable with the clutch pedal, and an interlocking mechanism including an interlocking member for transmitting a pivotal displacement of the clutch pedal to the control valve.
2. Description of the Related Art
In a tractor, a hydraulic clutch may be employed to connect and disconnect drive transmission from the engine to a drive transmission mechanism of a propelling system or PTO system. A clutch operating apparatus for operating the hydraulic clutch includes a clutch pedal supported to be pivotable when depressed, and a control valve with a linearly movable spool for controlling the hydraulic clutch. In order to transmit an operational displacement of the clutch pedal to the control valve, it has been considered to operatively interconnect the clutch pedal and the spool of the control valve through an interlocking mechanism having a link, rod, arm, lever and so on.
With the above clutch operating apparatus constructed to transmit an operational displacement of the clutch pedal as it is directly to the control valve, when the clutch pedal is not depressed, for example, pressure oil is supplied to the hydraulic clutch to maintain the clutch in a connected state (the state of transmitting drive from the engine to the drive transmission mechanism). By depressing the clutch pedal, the spool is pulled out and the pressure oil is drained from the hydraulic clutch to disconnect the clutch (i.e. to break the drive transmission from the engine to the drive transmission mechanism). However, in an operation requiring the clutch pedal to be depressed frequently, for example, it often is the case that the driver leaves his or her foot on a pedal portion of the clutch pedal even in situations where the clutch should be maintained in the connected state.
In such a case, the spool of the control valve could be operated by a load applied from the foot resting on the clutch pedal to the pedal portion of the clutch pedal unless a lost motion (play) is included in a range (stroke) of clutch depression. This would result in a pressure drop in the clutch pressure (i.e. clutch-connecting pressure) for the hydraulic clutch, causing the hydraulic clutch to xe2x80x9cslipxe2x80x9d. The lost motion noted above means that, even with a depression of the clutch pedal, its displacement is not transmitted to the control valve which therefore remains out of operation.
In the above clutch operating apparatus, besides providing no lost motion (play), a position of depression where a half-clutch state is recognizable is close to a depression starting position, compared with a conventional mechanical friction disk clutch. Consequently, the driver accustomed to operating the mechanical friction disk clutch has a sense of incompatibility and an unnatural feeling with respect to clutch operability.
Having regard to the state of the art noted above, the object of this invention is to provide a clutch operating apparatus for operating a hydraulic clutch, wherein a clutch pedal has play to avoid slipping of the clutch, and a half-clutch position in the second half of a stroke of the clutch pedal, to be operable with the same feeling as for operating an ordinary mechanical clutch.
The above object is fulfilled, according to this invention, by a clutch operating apparatus comprising a control valve for controlling pressure oil to connect and disconnect a clutch, a clutch pedal supported to be pivotable, a bracket pivotable with the clutch pedal, an interlocking mechanism including an interlocking member for operatively interconnecting the bracket and the control valve to operate the control valve with a pivotal movement of the clutch pedal, and a coupling mechanism for coupling the bracket and to one end of the interlocking member. The coupling mechanism includes a connecting pin disposed on one of the bracket and the interlocking member, and receiving bores formed in the other of the bracket and the interlocking member for receiving the connecting pin. The receiving bores are in form of slots shaped such that the clutch pedal has a lost motion only in an initial pivotal displacement thereof not to transmit the pivotal displacement to the control valve.
With the above construction, the coupling mechanism in the operational displacement transmission line extending between the clutch pedal and control valve involves a lost motion (play) only during an initial operational displacement of the clutch pedal. Thus, the driver is given the same feeling of operation as in operating a conventional mechanical clutch. With this lost motion (play), a clutch pressure drop may be avoided even when the driver keeps his or her foot resting on the pedal portion of the clutch pedal in repeating a clutch-connecting operation frequently.
As noted hereinbefore, the operational displacement transmission mechanism that transmits a pivotal displacement of the clutch pedal as converted to a displacement for operating the spool of the control valve tends to entail a problem that a smooth operational displacement transmission is impaired by twisting and the like. To avoid this problem, in one preferred embodiment of this invention, the interlocking mechanism is coupled to a spool of the control valve for transmitting an operational displacement thereto through a lever pivotable about a first axis, and the interlocking mechanism includes a relay mechanism pivotable about a second axis parallel to the first axis to transmit the operational displacement. In another embodiment, a guide member is provided for guiding the interlocking member so as to receive a sideways force applied to the interlocking member in time of transmitting an operational displacement. In a further embodiment, the interlocking member has a spring for acting to oppose a sideways force applied to the interlocking member in time of transmitting an operational displacement.
In any case, such a structural feature of the operational displacement transmission line assures a smooth operation of the spool of the control valve for connecting and disconnecting the clutch even where the spool is operated by a pivotal movement of a lever pivotable about an axis not parallel to the pivotal axis of the clutch pedal. Thus, the spool is never stalled or stuck when the clutch pedal is depressed.
Other features and advantages of this invention will be apparent from the following description of the embodiment to be taken with reference to the drawings.